Mixed lipid-bicarbonate colloidal particles

ABSTRACT

A composition is disclosed containing non-esterified fatty acids having 14-18 carbon atoms, monoglycerides which are monoesters of glycerol and fatty acids having 14-18 carbon atoms, lysophosphatidylcholine in which the fatty acid moiety has 14-18 carbon atoms and bicarbonate. The compositions can optionally also contain bile salts. These compositions form submicron size colloidal particles and can act as vehicles for transporting orally administered drugs, sources of calories in the form of readily absorbable fats and as particles for topical application to the skin. A method of making these particles is also described.

This is a continuation of co-pending application Ser. No. 07/567,243,filed on Aug. 13, 1990, now abandoned.

BACKGROUND OF THE INVENTION Drug Absorption

Drugs must reach their targets selectively and controllably if theirdesired pharmacological activities are to be maximized. One approach tooptimizing the activities of drugs is to control and sustain theirdelivery into the systemic blood circulation. Orally administered drugsare generally absorbed in the intestine. Such drugs undergo first passclearance by the liver and small intestine; that is, they are convertedby the intestine and the liver to pharmacologically inactive metabolitesand/or are secreted into bile by the liver, either as drug or as activemetabolites. As a result, the amount of an orally administered drugactually entering the systemic circulation can be much less than theamount administered. To ensure that effective quantities of such a drugwill enter the circulation and reach the targeted site(s) in the body,larger quantities than actually needed must be administered and oftenmust be given in several smaller doses, rather than one dose. Orallyadministered drugs also typically have poor bioavailability. Forexample, they may be adversely affected by the pH and the enzymaticactivity of the stomach and intestine and may be poorly dissolved in thestomach and intestinal fluids.

There have been numerous attempts to address these problems and toimprove the bioavailability of orally administered drugs. The efficacyof some drugs given orally has been improved by administering them witha triglyceride or neutral fat. Such fats represent an environment thatis compatible with lipophilic drugs, i.e. that exhibit low aqueoussolubility. Fats also enhance the stability of drugs which are unstablein the stomach and intestine. The end products of fat digestion areabsorbed by the villi of the intestinal mucosa into a lymphatic vessel,the central lacteal; absorption occurs within a region of the intestinein which limited drug metabolism occurs. The absorbed fat is transportedthrough the thoracic duct, the major lymphatic channel and issubsequently emptied into the blood; it is not carried in the portalblood, which goes to the liver, where first pass metabolism of drugsoccurs.

The absorption of griseofulvin has been shown to be enhanced if the drugis co-administered with a high fat content meal or in an oil and wateremulsion. Crounse, R. G., Journal of Investigative Dermatoloqy, 37:529(1961); Carrigan, P. J. and Bates, T. R., Journal of PharmacologicalScience, 62:1476 (1973). If the hormone testosterone undecanoate isadministered in a peanut oil solution, it is more biologically activethan if it is administered in an aqueous microcrystalline suspension.Coert, A. J. et al., Acta Endocrinol, 79:789 (1975); Hirschhauser, C. etal., Acta Endocrinol, 80:179 (1975). This effect is presumed to be dueto absorption of the steroid via the thoracic lymph rather than theportal blood; in this way, first pass clearance by the liver is avoided.

Cholesterol, its esters as well as triglyceride constituents (e.g.,fatty acids and monoglycerides) are absorbed via the thoracic lymph. Theeffects of some of these compounds, alone or in the presence of bilesalts, upon absorption of some orally administered drugs have beenevaluated. For example, oral administration of ubidecarenone, which isused for treating hypertension, in a mixture containing fatty acidshaving 12-18 carbon atoms and monoglycerides containing such fattyacids, resulted in somewhat greater absorption of the ubidecarenone thanoccurred after oral administration of the drug along (8.3% v. 2.3%).Taki, K. and Takahira, H., U. S. Pat. No. 4,325,942 (1982). If thesteroid progesterone is administered orally in combination withcholesterol or its esters, good sustained biological activity can beobtained. This is believed to be due to the absorption of progesteronevia the thoracic lymph and not via the portal circulation. Kincl, F. A.,Proceedings of the 6th International Congress of Pharmacology, 5:105(1975).

Yesair has evaluated the effect of fatty acids having 12-18 carbonatoms, monoglycerides of these fatty acids, and bile salts on theabsorption of orally administered estradiol, which is an estrogenichormone. Yesair, D. W., PCT WO 83/00294 (1983). The mole ratio of fattyacids:monoglycerides:bile salts evaluated ranged from 10:1:1, 1:1:10 or1:10:1. The preferred ratio was stated to be 2:1:2, which is similar tothe micellar composition resulting from the enzymatic digestion oftriglycerides in the intestine, which occurs in the presence of bilesalts and calcium ions. When excess bile salts are present, estradiolincorporated into the 2:1:2 composition can migrate or partition into abile salt-enriched micellar solution. This migration or partitioning ofestradiol occurred prior to absorption of the drug, as shown by the factthat the initial concentrations in plasma of estradiol are initiallygreater than those in lymph. In addition, about 25-50% of the estradioladministered in the composition was co-absorbed with the lipidconstituents and entered the systemic circulation via the thoraciclymph.

The presence of bile salts, which are absorbed in the ileum (and not inthe jejunum, as is most fat) compromised the co-absorption of estradiolwith fat by enhancing the migration of the drug from fat to the bilesalt micelle. Phosphatidylcholine was used in an effort to maintain theestradiol within the micellar composition in which fattyacids:monoglycerides:bile salts occurred in a 2:1:2 molar ratio. In thepresence of excess bile salts, about 60% of the estradiol incorporatedinto the 2:1:2 micellar composition remained associated with it whenphosphatidylcholine was not present. Under the same conditions, about70-75% of the estradiol remained in the composition whenphosphatidylcholine was used. Addition of phosphatidylcholine for thispurpose, however, results in an increased size of the delivery system.Size is an important parameter in the absorption of lipid micelles andthis effect of phosphatidylcholine might interfere with co-absorption ofthe drug with the lipids. In addition, excess phosphatidylcholine hasbeen shown to reduce lipid absorption. Ammon, H. V., et al., Lipids,14:395 (1979); Clark, S. B., Gastrointestinal Physiology, 4:E183 (1978).

Others have also described the effects of the presence of bile salts inlipid formulations used for co-absorption of drugs. Wilson, T. H., In:Intestinal Absorption, Saunders, (1962); Lack, L. and Weiner, I. M.,American Journal of Physiology, 240:313, (1961); H. V. Ammon et al.,Lipids, 14:395 (1979). For example, little difference in the absorptionof 5-fluorouracil (5FU) in the stomach or small intestine was evidentwhen the 5FU was administered alone or in a monoolein/sodiumtaurocholate mixed micelle formulation. 5FU absorption in the largeintestine was greater when the drug was administered in the formulationthan when it was administered alone. Streptomycin is poorly absorbedfrom the intestine. Muranushi and co-workers report that mixed micelles,composed of bile salts, monoolein or unsaturated fatty acids, did notimprove the absorption of streptomycin from the small intestine butmarkedly enhanced the absorption from the large intestine. Theenhancement in the large intestine was attributed mostly to thealteration of the mucosal membrane permeability by monoolein orunsaturated fatty acids. In contrast, mixed micelles of bile salts andsaturated fatty acids produced only a small enhancement in streptomycinabsorption even from the large intestine. Muranushi, N. et al., Journalof Pharmaceutics, 4:271 (1980). Taniguchi et al report thatmonoolein/taurocholate or oleic acid/taurocholate promotes theabsorption of heparin, which is poorly absorbed when administered alone.Taniguch, K. el at., International Journal of Pharmaceutics, 4:219(1980). Absorption of heparin from the large intestine was twice thatwhich occurred from the small intestine. The concentration of heparin inthe mixed micelle to produce the potentiation in the large intestine wasapproximately one-fourth that required in the small intestine.

In U. S. Pat. No. 4,156,719, Sezoski and Muranishi describe a micellesolution for rectal administration of water-soluble drugs that arepoorly absorbed. The composition consists of fatty acids having 6-18carbons, and/or mono- or diglycerides having the same type of fattyacids; a bile salt or other non-ionic surface activity agent; and water.A lysophosphatidylcholine moiety can be substituted for the fatty acidsand mono- or diglycerides. Absorption of streptomycin and gentamycinfrom the rectum and large intestine is reported to be comparable whenthe drug is administered in a bile salt:mixed lipid micelle. Similarformulations were not effective in increasing absorption in theduodenum. Muranushi, S. et al., International Journal of Pharmaceutics,2:101 (1979). Absorption of the two drugs via the rectum and largeintestine was markedly greater than that of a comparable doseadministered duodenally, even when the mixed lipid micelle concentrationadministered duodenally was four times that administered via the otherroutes.

In a patent to the present inventor (U. S. Pat. No. 4,874,795, Yesair)it was shown that a lipid composition with specific lipid components ina prescribed relationship to each other was effective in deliveringdrugs to the systemic circulation. The lipid composition included fattyacids having 14-18 carbon atoms, monoglycerides with a fatty acid moietyhaving 14-18 carbon atoms, and lysophosphatidycholine with a fatty acidmoiety having 14-18 carbon atoms. The fatty acid to monoglyceride molarratio could range from 2:1 to 1:2 and the mole percent oflysophosphatidylcholine could range from 30.0 to 1.0 when expressed asthe mole percent of the total lipid composition. This lipid compositionwas shown to effectively transport drugs to the systemic circulationwhen they were incorporated into the lipid composition. The lipidcomposition also was shown to serve as a source of calories by virtue ofits inherent fatty acid content that could be metabolized in anindividual's body.

Nutrition

Caloric requirements for individuals are primarily a function of bodycomposition and level of physical activity. Medically compromised, agedand physically stressed individuals often have limited body fat.Consequently, energy (caloric) needs will be satisfied mainly fromexogenous sources.

Physical activity uses muscle and the energy requirements of allmuscles, including the heart, are met primarily as a result of oxidationof fatty acids, from dietary fat or mobilized adipose fat. Adipose fatcan, as noted, be minimal and therefore efficient absorption of fat canbe an important consideration in satisfying the energy demands of themedically infirm, the aged and the physically active.

Fat absorption can be compromised in many circumstances. For example, incystic fibrosis, a disorder of exocrine glands, there is a deficiency ofpancreatic enzymes, bile salts and bicarbonate ions. Nutrition Reviews,42:344 (1984); Ross, C. A., Archives of Diseases of Childhood, 30:316(1955); Scow, R. O. E., Journal of Clinical Investigation. 55:908(1975). Fat absorption in cystic fibrosis patients can be severelyaffected and 30 to 60 percent of ingested fat can be malabsorbed. Themalabsorption and resulting steatorrhea are generally not successfullyhandled by the oral administration of pancreatic lipase. In an effort tocontrol the steatorrhea, the patient may consume less fat than desirablefor good health.

Fat absorption can be compromised under stressful conditions and thegenerally accepted way of addressing this problem has been to reduce fatconsumption. This approach can result in both acute and chronic medicalproblems. These problems might be avoided, or at least minimized, if areadily absorbable source of fat could be made available.

At the present time, there is a need for a more efficient method oftransporting orally administered drugs to the systemic circulation. Thisneed is particularly important for individuals with impaired oralintake, intestinal absorption or diminished transport capacity. At thesame time, there is a need for a more efficient oral administration ofcalorically rich substances, especially to individuals with acute energyrequirements. The achievement of such increased efficiencies wouldpromote more effective drug therapies and nutritional stability.

SUMMARY OF THE INVENTION

This invention relates to compositions for providing at least one drugor for providing readily absorbable calories to an individual. The basiccomposition of the present invention is comprised of: (1) at least onenon-esterified fatty acid having 14-18 carbon atoms, (2) at least onemonoglyceride which is a monoester of glycerol and a fatty acid having14-18 carbon atoms, (3) lysophosphatidylcholine in which the fatty acidmoiety has 14-18 carbon atoms, and (4) bicarbonate. An optional fifthcomponent of the composition is bile salts, which can be added to theother four components of the basic composition. The composition of thepresent invention is in the form of mixed lipid colloid particles, sincethey form a colloidal suspension in an aqueous environment. In thoseinstances in which components (1) through (4) are present in acomposition, the composition is referred to as a mixed lipid-bicarbonatecomposition (i.e., a mixed lipid- bicarbonate colloid) and in thoseinstances in which components (1) through (4) plus bile salt arepresent, the composition is referred to as a mixedlipid-bicarbonate-bile salt composition (i.e., a mixedlipid-bicarbonate-bile salt colloid). The bile salt component is addedwhen it is desired to further reduce the size of the particulate form ofthe basic composition from its inherent colloidal size.

In both types of compositions, the non-esterified fatty acid and theesterified fatty acid moieties of the monoglycerides andlysophosphatidylcholine can be saturated or unsaturated. If thenon-esterified fatty acids in the composition are saturated, sufficientquantities of divalent cations (approximately one-half the molar amountof the fatty acids), such as calcium ions, can optionally be added toform non-esterified fatty acid salts. These non-esterified fatty acidsalts would then form the non-esterified fatty acid portion of thecomposition.

The non-esterified fatty acids and the monoglycerides are present in thecomposition in a molar ratio of between about 2:1 and about 1:2(non-esterified fatty acid:monoglyceride). Taken together, thenonesterified fatty acids plus monoglycerides comprise from about 70.0mole percent to about 99.0 mole percent of the total lipid composition.The lysophosphatidylcholine therefore comprises from about 30.0 molepercent to about 1.0 mole percent of the total lipid composition.

The components of the composition of the present invention, namely thefatty acids, monoglycerides, lysophosphatidylcholine, bicarbonate, andoptionally, bile salts, can be combined to form a mixture before beingplaced in an aqueous environment. Preferably, however, the fatty acid,monoglyceride and lysophosphatidylcholine lipids of the basiccomposition are mixed together and then placed in an aqueous environmentfor the subsequent addition of bicarbonate, and optionally, bile salts.In either instance, following placement of the mixed components in theaqueous environment, the composition is further processed to form thecolloidal particles. For example, it can be subjected to a shearingoperation, mixed or stirred, sonicated or otherwise subjected to anappropriate force. To achieve these colloidal particles, thelysophophatydylcholine concentration of the lipid components (i.e., thesum of the concentrations of the individual lipid components) should beat least about 0.1 mM to ensure stable, mixed lipid particle formation.

The inclusion of bicarbonate in the basic mixed lipid-bicarbonatecomposition provides a means for controlling the size of the colloidalparticles formed as a result of the intermolecular forces between thecomponents of the composition in an aqueous environment. When the molarratio of bicarbonate to the lysophosphatidylcholine in the total lipidis about 1.4:1 or less, the mixed lipid-bicarbonate colloidal particlesize is approximately 120 nm or larger. When the molar ratio ofbicarbonate to the lysophosphatidylcholine in the total mixed lipidincreases from about 2:1 to about 7:1, the mixed lipid-bicarbonatecolloidal particle size decreases from approximately 120 nm toapproximately 70 nm in direct relationship to the increase in molarratio of bicarbonate to lysophosphatidylcholine in the total mixedlipid. If the molar ratio of bicarbonate to lysophosphatidylcholine inthe total mixed lipid is increased beyond about 7:1, there is no furtherdecrease in mixed lipid-bicarbonate colloidal particle size.

When bile salts are additionally incorporated into the lipid-bicarbonatecomposition, the resulting mixed lipid-bicarbonate-bile salt colloidalparticle size is smaller than the mixed lipid-bicarbonate colloidalparticle size. For example, if the molar ratio of bicarbonate to thelysophosphatidylcholine in the total mixed lipid is at least about 7:1and the molar ratio of bile salt to the lysophosphatidylcholine in thetotal mixed lipid is at least about 10:1, the mixed lipid-bicarbonate-bile salt colloidal particle size is about 10 nm or less.

The compositions of this invention are designed to promote uptake of themixed lipid colloid of the lipid formulations into the mucosa of thesmall intestine, subsequent synthesis into chylomicrons, translocationof the chylomicrons to the thoracic lymph and eventual transport to thesystemic circulation (i.e., the blood stream). The compositions whichare the subject of this invention have several characteristics whichwill promote rapid and quantitative absorption of lipids in the smallintestine and transport of lipids via the lymphatic system. First, themole ratio range described for the fatty acids and monoglycerides isoptimal for their absorption in the jejunum. Second, the unsaturatedfatty acids or saturated fatty acid-calcium salts included in thecompositions have been shown to be maximally absorbed and preferentiallytransported via the thoracic lymph rather than via the portal blood.Third, the compositions contain lysophosphatidylcholine which enhancestranslocation of the lipid particles as chylomicrons into the thoraciclymph. Fourth, the reduction in size of the lipid particles allows theexistence of more particles per unit volume and promotes ease of masstransport of the individual particles. This reduction in size of theparticles also allows a higher concentration of organized lipidparticles to exist in an aqueous environment.

The mixed lipid compositions which are the subject of this invention canserve as a transport vehicle for enhanced uptake and bioavailability ofa drug or drugs. Drugs are broadly defined here as any chemical agentsor chemical substances which affect living processes. These chemicalsubstances can become integrally incorporated into the basic lipidparticles. Examples of substances which can be incorporated into thebasic composition of this invention are drugs administered fordiagnostic, therapeutic or preventive purposes, lipophilic pro-drugs,bioactive peptides and other xenobiotics. Other such substances includevitamins, e.g., fat-soluble vitamins, and other like materials ofmetabolic or nutritive value. The enhanced uptake occurs because thesubstance incorporated into the compositions of this invention isabsorbed together with the lipids and subsequently enters the systemiccirculation via the lymphatic system. The substance is absorbed morerapidly and more completely than it otherwise would be because firstpass clearance by the liver is avoided. Thus, more of the absorbed doseenters the blood and is available to reach target sites within anindividual's body than would be available if the mixed lipid-bicarbonateformulations were not used.

The subject compositions can also serve as highly concentrated sourcesof readily absorbable fat, which can be used, for example, by thoseindividuals in need of a calorically dense dietary component. When usedin this manner, the compositions of the present invention generally donot include a drug and are comprised of the nonesterified fatty acids,monoglycerides and lysophosphatidylcholine. They can, for example,include a fat soluble vitamin.

The subject compositions also provide stable mixed lipid colloids thatprotect incorporated drugs from, for example, enzymatic and chemicaldegradation in the stomach and upper intestine. In addition, theinherent stability of the lipid components of the compositions make thecompositions stable over extended periods of time and thus can serve asstable delivery vehicles for the substances incorporated into the mixedlipidbicarbonate formulations.

The subject mixed lipid compositions can be produced according to thefollowing method: In the preferred embodiment, the method includes thefollowing steps: First, the following components are combined in a non-aqueous environment: (1) at least one non-esterified fatty acid having14-18 carbon atoms, (2) at least one monoglyceride which is a monoesterof glycerol and fatty acid having 14-18 carbon atoms, and (3)lysophosphatidylcholine in which the fatty acid moiety has 14-18 carbonatoms. The non-esterified fatty acids, monoglycerides andlysophosphatidylcholine are mixed together in molar ratios as describedabove and then placed in an aqueous environment containing thebicarbonate component. Second, the mixed lipid composition is subjectedto shearing forces of sufficient energy and for sufficient time forlipid particles of uniform size to form. The shearing forces producecavitation of the aqueous environment containing the lipid andbicarbonate components such that these components segregate intoparticles. The results of this shearing operation are mixedlipidbicarbonate colloidal particles of a homogeneous, uniform size.

The shearing forces may be applied as the bicarbonate is being added tothe mixed lipid-aqueous mixture or they can be applied after thebicarbonate has been added to achieve a specified molar ratio ofbicarbonate to total mixed lipid. In either case, the same mixedlipid-bicarbonate colloidal particle size results.

The same method is used to produce the mixed lipid-bicarbonate-bile salecompositions of the present invention. Again, the bile salt can be addedbefore or during the shearing operation. The same mixedlipidbicarbonate-bile salt colloidal particle size is achieved in eitheroccurrence.

The bicarbonate and bile salt can be added to the lipid mixture in theaqueous environment either simultaneously or sequentially. The order inwhich they are added is not critical. The same uniform mixedlipid-bicarbonate-bile salt colloidal particle size is achievedregardless of which order the bicarbonate and bile salt are added. Toachieve the 10 nm or less mixed lipid-bicarbonate-bile salt colloidalparticle size, the proper molar ratios of bicarbonate to total mixedlipid and bile salt to total mixed lipid must be attained before thefinal shearing operation.

The above identified lipid particles can also be formed whenbiologically compatible surfactants, such as TWEEN 80, are added to theabove formulations. The addition of such surfactants does not impede theformation of the mixed lipid-bicarbonate or mixed lipid-bicarbonate-bilesalt colloidal particles.

A drug or drugs can be administered to an individual by oraladministration of a mixed lipid-bicarbonate composition of the presentinvention in which the drug (or drugs) is incorporated. Likewise,calories in the form of fatty acids, monoglycerides orlysophosphatidylcholine can be delivered to individuals by orallyadministering the above mixed lipid-bicarbonate compositions. In eithercase, bile salts can optionally be a component of the mixed lipidbicarbonate composition to form mixed lipid-bicarbonate-bile saltcompositions that can be administered orally to an individual.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the relationship between the surface tensionof the mixed lipid formulation and the molar concentration of thelysophosphatidylcholine (and mixed lipids) in the mixed lipidformulation.

FIG. 2 is a graph showing the relationship between the particle size orsurface tension of the mixed lipid formulation and the amount of sodiumbicarbonate in the aqueous environment.

FIG. 3 is a graph showing the relationship between the particle size ofthe mixed lipid formulation and the amount of bile salt, sodiumtaurocholate, in the aqueous environment.

FIG. 4 is a graph showing the relationship between the particle size orsurface tension of the mixed lipid formulation and the combination ofbicarbonate and bile salt, sodium taurocholate.

FIG. 5 is a graph showing the elution profiles from a Sepharose 4Bcolumn of the mixed lipid (fenretinamide)-bicarbonate, mixedlipid(fenretinamide)bicarbonate-bile salt and of free fenretinamide.

FIG. 6 is a graph showing the elution profiles from a Sepharose 4Bcolumn of the mixed lipidbicarbonate formulation and the mixedlipid-bicarbonate-bile salt formulation containing diltiazem (Drug A)and hydrochlorothiazide (Drug B).

DETAILED DESCRIPTION OF THE INVENTION

The composition of the present invention is comprised of non-esterifiedfatty acids, monoglycerides of those fatty acids,lysophosphatidylcholine having those fatty acids as their fatty acidmoiety, and bicarbonate. The selection of the components of the subjectcomposition is based on the absorption and transport characteristics ofthe fatty acids, the contribution of lysophosphatidylcholine tosolubilization of drugs in the lipid composition, the properties ofbicarbonate that allow stable, submicron size lipid-containing particlesto exist and to translocation of absorbed fat into the lymph (ratherthan into the portal circulation).

Absorption of saturated fatty acids has been shown to be inverselyrelated to the number of carbon atoms in the fatty acid. For example,absorption of decanoic (10:0, which denotes chain length and degree ofunsaturation) is almost quantitative. For lauric (12:0), it is more than95%; for myristic (14:0), 80-90%; for palmitic (16:0), 65-70% and forstearic (18:0), 30-45%. Absorption of unsaturated fatty acids into lymph(e.g., linoleic 18:2) have been shown to be more rapid and to a greaterextent than are saturated fatty acids. Taniguchi, K., InternationalJournal of Pharmaceutics, 4:219 (1980).

Transport of absorbed fatty acids via the lymph (and not in the portalcirculation) varies greatly. That is, a much larger percentage ofabsorbed unsaturated fatty acids has been shown to be carried in thelymph than is the case for saturated fatty acids. About 85% ofunsaturated fatty acids has been shown to be carried in the lymph.Miura, S. et al., Keio Journal of Medicine, 28:121 (1979). The amount ofthese absorbed fatty acids being carried in the lymph is also inverselyrelated to chain length: 68-80% for myristic; 85% for palmitic andstearic.

If saturated fatty acids are included in the composition of thisinvention, they can be included as calcium salts or salts of anothercation. This is true because the enzymatic hydrolysis of triglycerides,which releases saturated fatty acids, favors their calcium soapformation. Tak, Y. A. and Grigor, M. R., Biochimica Biophysica Acta,531: 257 (1978).

Translocation of absorbed fat into the lymph has been shown to requirelysophosphatidylcholine. The rate, but not the magnitude, of thetranslocation of absorbed fat is apparently related to the fatty acidmoiety of the lysophosphatidylcholine. For example, oleoyllysophosphatididylcholine results in a 100% increase in triglyceride andphospholipid in lymphatic transported fat when compared with the effectsof a lysophosphatidylcholine derived from a phosphatidylcholine composedmainly of saturated fatty acids (e.g., palmitic, C16:0; stearic, C18:0).Incorporating an unsaturated lysophosphatidylcholine into thecompositions of this invention will enhance the translocation of theabsorbed lipids and the co-absorbed drugs or other substances. Inaddition, lysophosphatidylcholine plays a role in the solubilization ofsome drugs (i.e., its presence enhances the solubility of the drugs inthe compositions).

Examples of unsaturated fatty acids which can be used in the compositionof this invention are:

    ______________________________________                                        palmitoleic      C.sub.16 H.sub.30 O.sub.2                                                              16:1                                                oleic            C.sub.18 H.sub.34 O.sub.2                                                              18:1                                                linoleic         C.sub.18 H.sub.32 O.sub.2                                                              18:2                                                linolenic        C.sub.18 H.sub.30 O.sub.2                                                              18:3                                                ______________________________________                                    

Examples of saturated fatty acids which can be used in the subjectcomposition are:

    ______________________________________                                        myristic        C.sub.14 H.sub.28 O.sub.2                                                              14:0                                                 palmitic        C.sub.16 H.sub.32 O.sub.2                                                              16:0                                                 stearic         C.sub.18 H.sub.36 O.sub.2                                                              18:0                                                 ______________________________________                                    

The unsaturated and saturated fatty acids can be present individually orin combination. That is, the fatty acid constituents of one or more ofthe lipid components (fatty acid, monoglyceride andlysophosphatidylcholine) can be identified or they can be a mixture ofthe unsaturated and/or saturated members of the preferred fatty acidfamilies.

The non-esterified fatty acids and monoglycerides are present in amountswhich result in a molar ratio of from about 2:1 to about 1:2(non-esterified fatty acid: monoglyceride).

In addition, the compositions have lysophosphatidylcholine, the fattyacid moiety of which has 14-18 carbon atoms and is preferablyunsaturated. The fatty acid constituent of the lysophosphatidylcholineis preferably one of those listed above. The quantity oflysophosphatidylcholine in the composition is determined by the amountneeded for enhanced solubilization of a drug to be administered in thecomposition and the amount needed for its role in translocation. Ingeneral, lysophosphatidylcholine choline comprises from about 1.0 mole %to about 30.0 mole % of the total composition. The fatty acids whichcomprise the compositions of this invention--whether as nonesterifiedfatty acids or as constituents of monoglycerides orlysophosphatidylcholine--can all be the same or a number of differentones can be included.

Lipid formulations including the fatty acids, monoglycerides andlysophosphatidylcholine described above will swell in the presence ofdistilled water when heated and hand-shaken. Eventually, a gelatinousmatrix is yielded that appears to be crystalline when viewed under apolarizing microscope. In the presence of 0.1 N HCl or pH 7.0 phosphatebuffer, these lipid formulations do not appear to swell in the presenceof distilled water when heated and hand-shaken, but remain as largeoil/solid particles in these solutions. In contrast, these lipidformulations in the presence of distilled water and aqueous bile salts,with heat and hand-shaking, yield micron sized particles when viewedunder a polarizing microscope. A conclusion that can be drawn from theseobservations is that the ionic species in the aqueous medium affect thesize and constitution of particles formed from these lipid formulations.In particular, the anion types can significantly alter lipid particleformation, constitution and size.

It is known that, in addition to bile salts, the principal anion in theupper region of the small intestine is bicarbonate. It has been foundthat when this anion is present in sufficient quantities in the aqueousmedium of the lipid formulations, submicron particles can be formed. Thebicarbonate is incorporated in the compositions of the present inventionby directly mixing the bicarbonate with the lipid components, or,preferably, by dissolving salts of this anion, such as sodiumbicarbonate, potassium bicarbonate, etc., in the aqueous environment towhich the previously mixed lipid components of the compositions havebeen placed. When the mixed lipid colloidal particles are formed by theshearing operation, bicarbonate is integrally included in theparticulate form of the compositions.

If bile salts are additionally present in sufficient quantities in theaqueous environment, the already submicron particles can be even furtherreduced in size. Examples of bile salts that will reduce the size of themixed lipid-bicarbonate colloidal particles are sodium taurocholate andsodium glycocholate. The bile salts can be added to the non-aqueousmixed lipid-bicarbonate mixture, or, preferably, are added to theaqueous environment in which the lipid components and bicarbonate havebeen combined. The bile salts then become incorporated in the colloidalparticles of the compositions when these particles are formed by theshearing operation.

The compositions of this invention are preliminarily made according tothe following method. The component lipids are weighed and mixed, withor without heat, to attain liquid homogeneity. When a drug isincorporated, it is added and dissolved, with or without heat, in thelipid mixture. A uniform state is indicated by the absence of any solidsat the appropriate temperature for the mixture to be a liquid and by theabsence of any schleiren. A schleiric effect will be more apparent atgreater concentrations of the drug in the lipid mixture if it isincluded. The formulation is stable to several freeze-thaw cycles; theappearance of solids or schleirin may indicate instability of theformulation.

A second preliminary method of making the formulation involvesdissolving the component lipids and drug, if it is incorporated, in asolvent or mixture of solvents and mixing to attain homogeneity. Thesolvents are removed, in vacuo or by other suitable methods. Thecriteria for a suitable formulation are the same as noted above.

A desired amount of an above preliminary formulation is placed in anaqueous environment. This aqueous environment is predominately water.Other substances can be present without altering the basic compositions.Examples of these other substances are pH buffering materials, aminoacids, proteins, such as albumin or casein, and viscosity enhancers suchas xanthine gums or gum arabic. The only criterion for the presence ofthese other substances is that they not substantially interfere with oralter the forces which cause the individual components of thecomposition to form the colloidal particles of the composition.

Bicarbonate is added to the aqueous environment by dissolving a desiredamount of bicarbonate salt in the aqueous environment either before orafter the preliminary formulation has been placed there.

The component lipid mixture in the aqueous environment is then subjectedto shearing forces by an appropriate means. Typically, these shearingforces are achieved with a sonicator or a microfluidizer. The shearingoperation is performed at an appropriate energy and for a timesufficient to yield homogeneous lipid-containing particles of thedesired size. As noted in a below exemplification, the amount ofbicarbonate relative to the amount of lipid formulation is important indetermining the ultimate size of the mixed lipid-bicarbonate colloidalparticles. Below a molar ratio of 1.4:1 (bicarbonate:mixed lipidformulation) the mixed lipid bicarbonate colloidal particle size will belarger than approximately 120 nm. Between a molar ratio of 1.4:1 and7:1, the mixed lipid-bicarbonate colloidal particle size will be betweenapproximately 120 nm and approximately 70 nm, depending on the molarratio of bicarbonate to mixed lipid formulation. The bicarbonate can beadded gradually or all at one time as the shearing procedure isperformed. Alternatively, the bicarbonate can be added before theshearing procedure is performed.

To obtain smaller submicron particles, bile salts at an appropriatemolar ratio (bile salt:mixed lipid formulation) can be added to theaqueous medium before, concurrently, or after the bicarbonate is added.The molar ratios of bile salt to mixed lipid formulation as well asbicarbonate to mixed lipid formulation can be any independent value,provided each of them is at least about 1:1 (i.e., the bile saltconcentration or the bicarbonate concentration should be at least thesame as the mixed lipid concentration). That is, the bile salt:mixedlipid formulation molar ratio as well as the bicarbonate:mixed lipidformulation molar ratio can be independently changed, resulting in anaccompanying change in the mixed lipid-bicarbonate-bile salt colloidalparticle size. However, to achieve mixed lipid-bicarbonate-bile saltcolloidal particles of 10nm or less, the molar ratio of bile salt tomixed lipid formulation should be at least about 10:1 and the molarratio of bicarbonate to mixed lipid formulation should be at least 7:1.Again, the bile salts can be added gradually or all at one time beforeor while the shearing operation is performed.

As previously noted, compositions of the present invention can alsoinclude a drug, which is any chemical agent or chemical substance whichaffects living processes. They include, but are not limited to, drugsadministered for diagnostic, therapeutic or preventive purposes;lipophilic pro-drugs; nutrients, such as fat soluble vitamins, and otherxenobiotics.

Biologically compatible surfactants can be added at any time to theaqueous medium containing the lipid formulation and bicarbonate(optionally also containing the bile salt). Examples of biologicallycompatible surfactants include TWEEN 20, TWEEN 80, etc. Thesesurfactants can be added before or after the shearing operation.

The mixed lipid-bicarbonate or the mixed lipidbicarbonate-bile saltcolloidal particles are stable and can be stored under normal storageconditions. When a drug is incorporated in either of these compositions,the colloidal particles serve as a vehicle for transporting the drug tothe intestinal mucosal cells following oral administration of thedrug-containing particles to an individual. These drug-containingcolloidal particles can be packaged, for example, in individualcontainers for oral administration of specific dosages of theincorporated drug. An individual simply opens the packaging containerand swallows its contents to achieve the oral administration of thedrug-containing colloidal particles.

Likewise, the mixed lipid-bicarbonate or the mixedlipid-bicarbonate-bile salt compositions can serve as a source ofcalories when administered without an incorporated drug. Again, anindividual simply swallows the contents of a container that has aspecific amount of the mixed lipid formulation to achieve oraladministration of the desired composition.

The mixed lipid-bicarbonate or the mixed lipid-bicarbonate-bile saltcompositions, with or without a constituent drug, also can be topicallyapplied to the skin of an individual. Such application provides a sourceof lipids, and drug if included, to the skin surface for whateverpurpose is desired.

The present invention is illustrated by the following examples which arenot intended to be limiting of the invention.

EXAMPLE 1 Formation of Submicron Sized Particles of Lipid Formulations

The following lipids were mixed together to yield a non-aqueous lipidmixture: soy lysophosphatidylcholine (LPC), 18:1 monoolein monoglyceride(MG), and 18:1 oleic acid fatty acid (FA). The sources of these lipidswere: Avanti Polar Lipids, 5001A Whitling Drive, Pelham, AL 35124 forLPC, and Nu-Chek-Prep, Inc., P. 0. Box 295, Elysian, MN 56028 for MG andFA. The molar ratio of these lipid components was 1:3:3 for LPC:MG:FA.This non-aqueous lipid mixture was put into water at LPC concentrationsranging from 10⁻³ to 1 mM. Since the molar ratio of LPC:MG:FA was 1:3:3,the total lipid mixture molar concentrations also ranged from 10⁻³ to 1mM in the water environment. These formulations were then subjected toprobe sonication (Cole-Parmer, 4710 Series with a S&M 10 86 tip, 1.25minutes at full power output). The surface tension (dynes/cm) of thesemixed lipid formulations was measured by determining the time betweendrops. Using this technique, the critical micelle concentration of thismixed lipid formulation was found to be about 0.1 mM (See FIG. 1).

Particle sizes were measured of a 1.5 mM concentration of LPC (and alsototal lipid mixture) of the 1:3:3 LPC:MG:FA formulation in water afterprobe sonication was performed. The particle sizes were measured witheither a Nicomp Analyzer or a Brookhaven Particle Sizer. After theinitial probe sonication, the particle size was approximately 170 nm.Sodium bicarbonate, NaHC03, was incrementally added, sonication wascontinued and particle size was monitored. As the molar ratio ofbicarbonate to lipid formulation (bicarbonate:lipid) approached 1.4:1,the particle size approached approximately 120 nm. When thebicarbonate:lipid molar ratio was increased to 7:1, the particle sizedecreased to approximately 70 nm. Between these bicarbonate:lipid molarratios, intermediate size particles of the lipid formulation wereobserved (see FIG. 2). As the bicarbonate:lipid molar ratio was furtherincreased, the particle size did not significantly change.

In another experiment, soy lysophosphatidylcholine, 18:1 monooleinmonoglyceride, and 18:1 oleic acid fatty acid from the same sources asin the first experiment were mixed together to yield a non-aqueous lipidmixture with a molar ratio of 1:3:3 LPC:MG:FA. The non-aqueous lipidmixture was put into water so the LPC (and also total lipidmixture)molar concentration was about 1.7 mM. This formulation was thensubjected to either probe sonication (Cole-Parmer sonicator) or shearingby action of a Microfluidizer (Model 110T, 2 passes at 70 psi). Afterthe shearing operation, the particle size was approximately 150 nm forthe 1:3:3 formulation. The bile salt, sodium taurocholate, was graduallyadded and shearing was continued. The particle size was monitored as thebile salt was added. The particle size was reduced to approximately 100nm while the bile salts were in their monomeric state (i.e., less thanabout 5 mM) and the molar ratio of bile salt to mixed lipid was about5:1. As more bile salt was added, the particle size for this formulationdecreased to approximately 50 nm when the bile salts were primarily intheir micellar state (i.e., greater than about 5 mM) and the molar ratioof bile salt to mixed lipid was about 9:1. Between these bile salt:mixedlipid molar ratios, intermediate size particles of the lipidformulations were observed (see FIG. 3).

When bicarbonate was added with sonication to the formulations of thelatter experiment, the particle size was further reduced toapproximately 10 nm or less as the bicarbonate:lipid molar ratio wasincreased to at least 7:1. When the bile salt, sodium taurocholate, wasadded with sonication to the formulation of the second experiment, theparticle size was further reduced to approximately 10 nm or less as thebile salt:lipid molar ratio was increased to 10:1, i.e., as the bilesalts reached their critical micellar concentration (achieving themicellar state). That is, when both the bicarbonate ion and bile saltreached their optimal concentrations for forming the smallest sizeparticles of the lipid formulations, the particle size was approximately10 nm or less (see FIG. 4, where the concentration of LPC, and alsototal lipid mixture, was about 2.7 mM for the 1:3:3 LPC:MG:FAformulation).

EXAMPLE 2 Incorporation of Drugs in the Colloidal Particles

Fenretinamide was formulated with the mixed lipid LpC:MG:FA (1:3:3 molarratio) using the solvent method of preparation. The molar concentrationof fenretinamide was 0.8 with respect to LPC (and also total lipidmixture) in the mixed lipid(drug) formulation. This non-aqueous mixedlipid(drug) formulation was put into an aqueous environment so the LPC(and also total lipid mixture) concentration was about 1.3 mM. Theaqueous environment contained either bicarbonate at a concentration of12.5 mM (i.e. a molar ratio of about 10:1 for bicarbonate:(LPC in mixedlipid) or bicarbonate and bile salt at respective concentrations of 12.5mM (i.e. molar ratios of 1:10:10 for LPC in mixed lipid:bicarbonate:bilesalt). Colloidal particles of this mixed lipid (fenretinamide) withbicarbonate or with bicarbonate and bile salt were made by the methoddescribed in Example 1. This drug is hydrophobic in nature and tends toreside in the hydrocarbon region of the mixed lipid-bicarbonate or mixedlipid-bicarbonate-bile salt formulations. Upon size exclusionchromatography on a Sepharose 4B column, the drug remained associatedwith the mixed lipid-bicarbonate or with the mixedlipid-bicarbonate-bile salt particles (see FIG. 5). Free drug, i.e.,without the presence of the particles, eluted from the column with adistinct elution profile in the region identified as `free drug` in FIG.5. The smaller size of the mixed lipid(drug)-bicarbonate-bile saltparticles compared with the the mixed lipid(drug)bicarbonate particlesis noted from the longer retention before elution from the sizeexclusion column.

Diltiazem, a benzothiazepine, was formulated with the mixed lipidLPC:MG:FA (1:3:3 molar ratio) using the solvent method of preparation.Colloidal particles of this mixed lipid(diltiazem) formulation witheither bicarbonate or bicarbonate and bile salt were made by the methoddescribed in the preceding experiment. This drug is hydrophobic innature and tends to reside in the hydrocarbon region of the mixedlipid-bicarbonate formulations. Upon size exclusion chromatography on aSepharose 4B column, the drug remained associated with the mixedlipid-bicarbonate particles as well as with the mixedlipid-bicarbonate-bile salt particles. Free drug, i.e. without thepresence of the particles, eluted from the column with a distinctelution profile when compared with the drug associated with the mixedlipid-bicarbonate particles. (See Drug A and `Free Drug` of FIG. 6).

In a separate experiment, hydrochlorothiazide (HCTZ) was formulated withthe mixed lipid LPC:MG:FA (1:3:3 molar ratio) using the solvent methodof preparation. This drug is not soluble per se with just monoglyceridesand fatty acids. However, colloidal particles of this mixed lipid(HCTZ)formulation with bicarbonate were made by the method described in thefirst experiment of this Example. Size exclusion chromatography of thesemixed lipid(HCTZ)-bicarbonate particles on a Sepharose 4B column showedthe elution profile of HCTZ as free HCTZ. This indicates that HCTZprobably resides in the polar regions of the mixed lipid-bicarbonateformulations and becomes free drug when bicarbonate is present. Next,the mixed lipid(HCTZ) formulation and mixed lipid(diltiazem) formulationof the preceding experiment were mixed together at about a 1:5 weightratio of the respective formulations. This `super mixture` was thensonicated in either an aqueous bicarbonate solution or an aqueousbicarbonate-bile salt solution and the resulting materials were elutedby size exclusion chromatogrphy from a Sepharose 4B column. Mixed lipid(diltiazem)-bicarbonate colloidal particles or mixed lipid (diltiazem)-bicarbonate-bile salt colloidal particles (Drug A in FIG. 6) and freeHCTZ (Drug B in FIG. 6) were eluted. These results show that with thistechnique of making mixed lipid(drug)-bicarbonate colloidal particles ormixed lipid(drug)-bicarbonate-bile salt colloidal particles, togetherwith size exclusion chromatography, one can approximate the stability ofmixed lipid-drug formulations to the milieu of the GI tract.

EXAMPLE 3 Skin Application of the Colloidal Particles

The mixed lipid formulation of Example 1 was additionally mixed withcasein (1-2% casein by weight in the lipid mixture) or with visible orfluorescent dyes. Colloidal particles of mixtures with bicarbonate weremade by the method described in Example 1. These colloidal particleswere topically applied to the skin. Following this application, thecolloid lipids that resided on the skin surface gave a desirable tactilesensability, e.g., softness, and repelled wetting of the skin surfacewith water. The colloidal particles that contained the visible orfluorescent dyes were solubilized from the skin surface by detergents.

Equivalents

Those skilled in the art will recognize, or be able to ascertain usingno more than routine experimentation, many equivalents to the specificembodiments of the invention described herein. Such inventions areintended to be encompassed by the following claims.

I claim:
 1. A composition for oral administration to an individualcomprising:a. at least one non-esterified fatty acid having 14-18 carbonatoms; b. at least one monoglyceride which is a monoester of glyceroland a fatty acid having 14-18 carbon atoms; c. lysophosphatidylcholinein which the fatty acid moiety has 14-18 carbon atoms; and d.bicarbonate; wherein said fatty acids and monoglycerides togethercomprise from about 70.0 mole percent to about 99.0 mole percent of thelipid composition and the molar ratio of said fatty acids to saidmonoglycerides, is from about 2:1 to about 1:2, and saidlysophosphatidylcholine comprises from about 30.0 mole percent to about1.0 mole percent of said lipid composition; and wherein the compositionis in the form of colloidal particles in an aqueous environment.
 2. Thecomposition of claim 1 wherein the concentration of saidlysophosphatidylcholine is at least 0.1 mM in said aqueous environmentand the molar ratio of said bicarbonate to said lysophosphatidylcholineis greater than 1:1 in said aqueous environment.
 3. The composition ofclaim 2 wherein the molar ratio of said bicarbonate to saidlysophosphatidylcholine is greater than 1.4:1.
 4. The composition ofclaim 3 wherein the molar ratio of said bicarbonate to saidlysophosphatidylcholine is greater than 7:1.
 5. The composition of claim4 which additionally comprises bile salts wherein the molar ratio ofsaid bile salts to said lysophosphatidylcholine in said aqueousenvironment is at least 10:1.
 6. The composition of claim 5 wherein saidbile salt is sodium taurocholate.
 7. A composition for oraladministration to an individual comprising:a. at least onenon-esterified fatty acid having 14-18 carbon atoms; b. at least onemonoglyceride which is a monoester of glycerol and a fatty acid having14-18 carbon atoms; c. lysophosphatidylcholine in which the fatty acidmoiety has 14-18 carbon atoms; and d. bicarbonate; wherein the molarratio of said fatty acids to said monoglycerides is about 1:1 and themolar ratios of said lysophosphatidylcholine to the sum of said fattyacids and said monoglycerides is about 1:6; and wherein the compositionis in the form of colloidal particles in an aqueous environment.
 8. Acomposition for oral administration to an individual produced by amethod comprising the steps of:a. combining a formulation comprising:i.at least one non-esterified fatty acid having 14-18 carbon atoms; ii. atleast one monoglyceride which is a monoester of glycerol and a fattyacid having 14-18 carbon atoms; and iii. lysophosphatidylcholine inwhich the fatty acid moiety has 14-18 carbon atoms; wherein the molarratio of said fatty acids to said monoglycerides is from about 2:1 toabout 1:2, and the amount of said lysophosphatidylcholine is from about1.0 mole percent to about 30.0 mole percent of the total lipid of theformulation; b. placing the combination of fatty acid, monoglyceride,and lysophosphatidylcholine in an aqueous environment containingbicarbonate; and c. subjecting said combination to shearing forcessufficient to cause said composition to form homogeneous, identifiablecolloidal particles.
 9. The composition of claim 8 further comprisingthe addition of bile salts to said aqueous environment before applyingsaid shearing forces, wherein the molar ratio of said bile salts to saidlysophosphatidylcholine of the formulation is at least 10:1.
 10. Amethod of delivering a readily absorbable source of calories derivedfrom free fatty acids, monoglycerides and lysophosphatidylcholine,comprising the oral administration of a composition comprised of:a. atleast one non-esterified fatty acid having 14-18 carbon atoms; b. atleast one monoglyceride which is a monoester of glycerol and a fattyacid having 14-18 carbon atoms; c. lysophosphatidylcholine in which thefatty acid moiety has 14-18 carbon atoms; and d. bicarbonate; whereinthe molar ratio of said fatty acids to said monoglycerides is from about2:1 to about 1:2, and said lysophosphatidylcholine comprises from about30.0 mole percent to about 1.0 mole percent of the total lipid in thecomposition; and wherein the composition is in the form of colloidalparticles in an aqueous environment.
 11. The method of claim 10 whereinsaid composition additionally comprises bile salts, wherein the molarratio of said bile salts to said lysophosphatidylcholine is at least10:1.